It is known to provide a movable gantry in a metalworking machine, such as a milling machine, in which the bed of the machine is stationary and the movable gantry is formed of heavy and massive steel construction to support one or more cutting heads mounted for longitudinal movement thereon. The cutting heads are also mounted on the gantry for vertical movement and the three-axis operation of the cutter is automatically controlled by a numerical control system for computerized commands stored on a magnetic tape or the like.
In this type of metal working machine, the accuracy of the movement and/or positioning of the cutter is largely dependent upon the nonflexibility, stiffness or rigidity of the gantry and the workpiece supporting bed. The accuracy of the movement and positioning of the cutter is also dependent upon the accuracy with which the cutter is guided in its three-axis movements relative to the workpiece supporting bed. The massive size and weight of the gantry do provide the desired amount of rigidity but also limits the speed forward and rearward movement of the gantry when moving from one operating position to another, as well as the speed of movement during the actual cutting operation. With such a heavy and massive gantry, the time and distance required to accelerate from a stationary position to the desired speed, as well as the time and distance required to decelerate, requires that the machine be operated at a slower speed than is desirable.
The massive gantry also aids in preventing operational vibrations which, if permitted, cause the cutting tool to chatter and vibrate so that a smooth cut is not formed. The workpiece supporting bed is also usually formed of a massive block of solid steel to prevent operational vibrations in the workpiece supporting bed and the workpiece supported thereby. The heavy steel construction of the gantry and the workpiece supporting bed causes the machine to be very heavy and increases the cost of producing the machine.
Because of the massive size and relatively slow operational speeds of the known types of movable gantry metalworking machines, this type of machine is not economically suitable for and has not been adapted for use as a router/shaper woodworking machine for cutting furniture pieces and the like.